JP4996876B2 - High corrosion resistance aluminum alloy composite for heat exchanger and aluminum alloy heat exchanger - Google Patents

Description

  The present invention relates to an aluminum alloy composite material excellent in corrosion resistance and an aluminum alloy heat exchanger. More specifically, the present invention relates to an aluminum alloy composite material and an aluminum alloy heat exchanger that can be suitably used as heat exchanger components that are joined by brazing, such as automobile radiators, heaters, and evaporators.

Conventionally, brazing sheets with excellent corrosion resistance for heat exchangers are used for automobile radiators, heater cores, evaporator tubes, and plate materials, and an Al-Si brazing material is applied to one side of a core material made of an Al-Mn alloy. A three-layer aluminum alloy composite material is used which is clad and clad with an Al—Zn alloy made of an aluminum alloy which is baser than the core material as a sacrificial anode skin material on the other surface of the core material (for example, Patent Documents). 1).
Such an aluminum alloy composite Al-Si brazing material is used for joining a tube material and a fin material, and joining a tube material and a header plate at the time of brazing, and a sacrificial anode skin material is used as a core material and an electrochemical material. Due to the difference in properties, the skin material is mainly corroded, and the pitting corrosion of the core material is suppressed.
However, in recent years, the weight reduction of automobiles has been promoted due to environmental problems, and further demands for energy saving and cost reduction. Accordingly, weight reduction for automobile heat exchangers has been strongly demanded, and tube materials, fin materials Further, it has become necessary to further reduce the thickness of heat exchanger components such as plate materials. However, if various components are thinned and various elements are added to maintain a specific strength, the corrosion resistance may decrease or the corrosion life may decrease due to the thinning of the material. There was a need for materials for heat exchangers.
JP-A-5-318171

  An object of the present invention is to provide an aluminum alloy composite material for a heat exchanger and an aluminum alloy heat exchanger that have good corrosion resistance even when the thickness is reduced.

As a result of intensive studies in view of the above problems, the present inventors have a structure in which a specific V is contained in the sacrificial material, core material, or brazing material constituting the thinned heat exchanger constituting member. As a result of the construction, it was found that the progress of pitting corrosion, which is a problem as corrosion resistance, can be controlled, and the present invention has been made.
That is, the present invention
(1) In an aluminum alloy composite material for a heat exchanger having a sacrificial material layer, a core material layer, and a brazing material layer, the sacrificial material layer is 0.5 to 5 mass% Zn, 0.05 to 0.4 mass%. by weight of V, the balance being a sacrificial material layer made of Al and unavoidable impurities, and lower the high first solid solution phase and V concentrations of V concentrations in the sacrificial material layer a second solid solution phase and is double mixture member An aluminum alloy composite material for a heat exchanger having a structure in which the first phases in the stacking direction in the structure are alternately stacked in a thickness direction of 4 μm or more and 15 μm or less,
(2) In an aluminum alloy composite material for a heat exchanger having a sacrificial material layer, a core material layer, and a brazing material layer, the sacrificial material layer contains 0.5 to 5 mass% of Zn, and the balance is Al and inevitable It is a sacrificial material layer made of impurities, and the core material layer is 0.05 to 2.0 mass% Mn, 0.003 to 1.2 mass% Cu, 0.05 to 1.2 mass% Si, and 0.05. remainder containing ～0.4Mass% of V is Ri core layer der of Al and unavoidable impurities, and the first high Oite V concentration in the core layer a solid solution phase and V low concentration second Aluminum alloy composite material for heat exchangers having a structure in which a solid solution phase is alternately laminated in the thickness direction of the composite material, and the mutual interval between the first phases in the lamination direction in the structure is 4 μm or more and 15 μm or less ,
(3) In an aluminum alloy composite material for a heat exchanger having a sacrificial material layer, a core material layer, and a brazing material layer, the sacrificial material layer contains 0.5 to 5 mass% of Zn, and the balance is Al and inevitable It is a sacrificial material layer made of impurities, and the core material layer is 0.05 to 2.0 mass% Mn, 0.003 to 1.2 mass% Cu, 0.05 to 1.2 mass% Si, 0.05 remainder containing ～0.4Mass% of V and 0.03～0.3Mass% of Ti is Ri core layer der of Al and unavoidable impurities, and high Oite V concentration in said core layer first And a second solid solution phase having a low V concentration are alternately laminated in the thickness direction of the composite material, and the interval between the first phases in the lamination direction in the structure is 4 μm or more, above aluminum alloy composite material is 15μm or less, you (4) A member is produced using the aluminum alloy composite material according to any one of (1) to (3) above, and the member is brazed and heated at a temperature of 560 to 585 ° C. An aluminum alloy heat exchanger is provided.

  The aluminum alloy composite of the present invention has excellent corrosion resistance even in a severe corrosive environment in a thin state. Therefore, by using it for an aluminum alloy heat exchanger, it can contribute to weight reduction, and can provide long-term reliability.

The reasons for defining the content of the additive element in the present invention will be described below.
Vanadium (V) functions to improve the corrosion resistance of the sacrificial material or core material containing V. In other words, V is divided into a high-concentration region and a low region, and they are distributed alternately in the thickness direction to form a layer (lamination phase of solid solution), with the low-concentration region preferentially compared to the high region. Corrosion causes the corrosion form to be layered, preventing the progress of corrosion in the thickness direction, and as a result, the pitting corrosion resistance of the material is improved. If the V content is less than 0.05%, the effect is not sufficient. If it exceeds 0.4%, a coarse compound is produced at the time of casting, and the rolling process of the material is hindered. It becomes a progress point.

Next, the reason for adding each element other than V and the reason for defining the preferred content range will be described.
(1) Core material Mn in the core material dissolves in the matrix after brazing and is effective in improving strength. Furthermore, when used in combination with the inclusion of V of the present invention, it is very effective for the above-mentioned corrosion countermeasure to define the amount of Mn in the present invention. The reason why the preferable content of Mn is 0.05 to 2.0 mass% is that if it is less than 0.05 mass%, there is no effect in terms of improving the strength, and if it exceeds 2.0 mass%, the workability may decrease. It is. More preferably, it is 0.3 to 1.5 mass%.
The preferable content of Cu in the core material is set to 0.003 to 1.2 mass%. If the content is less than 0.003 mass%, there is no effect in the above aspect, and if it exceeds 1.2 mass%, the core material has self-corrosion resistance. This is because it may decrease and intergranular corrosion may be promoted. In addition, it is 0.005-0.5 mass% more preferably according to use environment.

If the Si content in the core material is less than 0.05 mass%, there is no effect in terms of strength improvement, and if it exceeds 1.2 mass%, deep pitting corrosion may occur due to single Si. More preferably, it is 0.3 to 0.9 mass%.
Zr and Ti in the core material are finely dispersed in the aluminum alloy as an intermetallic compound and have an effect of improving the strength. Therefore, Zr and Ti are added as necessary, but each is preferably 0.03 to 0.3 mass%. . If it is less than 0.03 mass%, the effect is not obtained. If it exceeds 0.3 mass%, solidification cracking at the time of casting may be induced. More preferably, 0.08 to 0.25 mass% is good for each.
Other elements may be contained as long as various properties are not deteriorated.

(2) Brazing material Since Si in the brazing material coexists with Al to form a low melting point compound, it is a basic composition for obtaining a brazing material having good fluidity. If the Si content in the brazing material is less than 5 mass% with respect to the total mass of the brazing material, the melting point of the brazing material becomes high, so that the predetermined fluidity cannot be obtained and the brazing property may be lowered. On the other hand, even when the Si content in the brazing material exceeds 15 mass%, similarly, the melting point of the brazing material becomes high, and there is a possibility that the predetermined fluidity cannot be obtained. Moreover, since coarse primary crystal Si is produced | generated, there exists a possibility that the workability of a brazing material may be inhibited. Therefore, the preferable Si content in the brazing material is 5 to 15 mass% with respect to the total mass of the brazing material.

  Cu in the brazing material lowers the melting point of the alloy and improves the brazing flow. Further, Cu has a function of enhancing the external corrosion resistance of the brazing material, and by the diffusion of Cu into the core material after the brazing treatment, it is expected that the strength of the core material is improved and the corrosion resistance is improved by forming a potential difference with the sacrificial material. However, from the point of corrosion resistance, a Cu content of 0.4 mass% or less cannot be said to be sufficiently effective, and in order to ensure stable brazing, a Cu content exceeding 1.0 mass% is necessary. More preferred. Moreover, if the amount of Cu exceeds 4.0 mass%, the brazing potential becomes too noble, the sacrificial material side may be extremely preferentially corroded, and the corrosion resistance may be lowered. There is also a possibility that the property may be lowered. Therefore, Cu is more preferably more than 1.0 mass% and 4.0 mass% or less, and particularly preferably 1.0 to 3.0 mass%, showing stable characteristics.

  The inclusion of Zn in the brazing material is preferable because it lowers the melting point of the alloy and stabilizes the brazing property. Further, it is preferable to contain Cu in order to perform the brazing treatment at a temperature of 560 to 585 ° C. In this case, the potential of the brazing becomes extremely noble than the potential of the core material, which may cause overcorrosion protection. The addition of Zn is preferable because it can give the brazing material an appropriate potential difference with respect to the potentials of the core material and the sacrificial material and improve the corrosion resistance at the same time. If the Zn content is 0.5 mass% or less, the effect is not sufficient. If it exceeds 2.0 mass%, the self-corrosion property of the braze may be lowered, and the rolling workability of the alloy may be lowered. In some cases, the brazing sheet for a heat exchanger may not be sufficiently satisfactory. Other elements may be added as long as various characteristics are not deteriorated.

(3) Sacrificial material The sacrificial material constituting the aluminum alloy composite of the present invention may be any material as long as it has the same action as the above-described sacrificial anode skin material, and an Al-Zn alloy is suitable. Zn has the effect of making the corrosion form a surface corrosion, has the effect of preventing the occurrence of pitting corrosion in the core material by lowering the potential of the sacrificial anode skin material and improving the sacrificial anode effect on the core material. If the content is less than 0.5 mass%, the sacrificial anode effect does not work sufficiently, which is not preferable. If the content exceeds 5 mass%, self-corrosion increases. Other elements may be contained as long as the sacrifice effect is not lowered.

  The aluminum alloy composite material for a heat exchanger of the present invention is an aluminum alloy composite material having a sacrificial material, a core material, and a brazing material, and is usually clad in the order of the sacrificial material, the core material, and the brazing material. However, a material having another function may be clad.

As for the manufacturing method of the sacrificial material, the core material, and the brazing material, casting is not limited to DC method, continuous casting strip (caster), or the like. Homogenization treatment conditions, hot rolling, cold rolling, intermediate annealing conditions and the like are not particularly limited, and can be appropriately determined by conventional methods. However, the tissue and the lower high first solid solution phase and V concentrations V concentration definitive sacrificing material layer or the core layer was contained V second solid solution phase were alternately stacked in the thickness direction of the composite material The manufacturing conditions are adjusted so that the mutual interval between the first phases in the stacking direction in the structure is 4 μm or more and 15 μm or less. By setting it as such a structure | tissue, the corrosion resistance of the sacrificial material layer or core material layer containing the said V becomes favorable.

  An aluminum alloy heat exchanger can be manufactured by brazing and heating the aluminum alloy composite of the present invention at a temperature of 560 to 585 ° C. The aluminum alloy composite material of the present invention can be used for a radiator of an automobile, a heater core, an evaporator tube, a plate material, etc., and any other member can be used as long as it is the same as the object of the present invention.

EXAMPLES Next, although this invention is demonstrated further in detail based on an Example, this invention is not limited to this.
Twenty-eight kinds of combinations of sacrificial material, core material, and brazing material having the composition shown in Table 1 were cast by die casting, and after both sides were cut, the sacrificial material started hot rolling at 500 ° C. Rolled to 5 mm. The brazing material was produced by a conventional method. The core material was homogenized at 520 ° C. for 6 hours, and finished to a thickness of 40 mm by chamfering. That is, the clad ratio of the sacrificial material to the entire composite material was set to 10%.
The sacrificial material, the core material, and the brazing material were stacked in this order, and hot rolling was started at 500 ° C. to obtain a three-layer clad material having a thickness of 3.5 mm. Thereafter, the thickness was reduced to 0.35 mm by cold rolling, subjected to intermediate annealing at 360 ° C. for 2 hours, and finally cold-rolled to a thickness of 0.25 mm to obtain a sample of an aluminum alloy composite material of H14.

These samples were subjected to heating at 570 ° C. for 3 minutes in a nitrogen gas atmosphere after applying a flux as Nocolok brazing heating treatment (NB heating) in the same manner as brazing conditions for manufacturing a heat exchanger. .
The obtained brazed sample was cut into a shape having a width of 30 mm and a length of 80 mm, and four sides from the end of the corrosion resistance test surface (sacrificial surface (front surface)) to a position 5 mm from the center, and the back surface The entire surface was sealed with a sealing tape to prepare a corrosion resistance test sample.

As described above, the alloy composites of the present invention (No1 , 4, 5, 7, 9-12, 14-17, 19, 20) and comparative alloy composites (No21 to 21) having the compositions shown in Table 1 below. 27) and a conventional alloy composite material (No. 28) were prepared. In the alloy composite of the present invention (No. 1 , 4, 5, 7, 9-12, 14-17, 19, 20), each material layer containing V has a first solid solution phase having a high V concentration and a V concentration. The low second solid solution phase had a structure alternately laminated in the thickness direction of the composite material, and the distance between the first phases in the lamination direction in the structure was 4 μm or more and 15 μm or less. On the other hand, the interval between the solid solution phases having a high V concentration is No. No. 21 to 23, 20 to 35 μm, no. 24-25, 1-2 μm, No. 27 was about 3 μm. Here, the length between the solid solution phases can be confirmed by polishing the cross-section of the sample plate, magnifying with an electron microscope, performing mapping analysis of V element with 10 visual fields by EPMA analysis, and mapping analysis with each visual field. The interphase spacing of the high V concentration part was measured and taken as the average value.

The following corrosion tests were conducted on these samples, and the pitting depth from the sacrificial material portion was measured.
(Corrosion test)
Liquid type: An aqueous solution of Cu ²⁺ 100 ppm, 5% NaCl adjusted to pH 3 with acetic acid was used as a corrosive solution.
Test conditions: Continuous spraying at about 50 ° C for 4 weeks

  The test results are shown in Table 2.

As is clear from the results of Tables 1 and 2 above, the samples of Comparative Example Alloy Composites Nos. 21 to 27 containing V, but the V content deviates from the range of the alloy composition defined in the present invention, are significantly corroded. In addition, in the sample of the conventional example not including V, a through hole is generated. In contrast, the samples of the present invention alloy composite Nos. 1 , 4, 5, 7, 9-12, 14-17, 19, 20 have good corrosion resistance with a pitting depth of 100 μm or less even in a severe corrosive environment, It can be confirmed that pitting growth is suppressed.

Claims (4)

In the aluminum alloy composite material for a heat exchanger having a sacrificial material layer, a core material layer, and a brazing material layer, the sacrificial material layer contains 0.5-5 mass% Zn, 0.05-0.4 mass% V. contained, the balance is the sacrificial material layer made of Al and unavoidable impurities, and a second solid solution phase low high first solid solution phase and V concentrations of V concentrations in the sacrificial material layer thickness of the double coupling member An aluminum alloy composite material for heat exchangers having a structure in which the layers are alternately stacked in a direction, and a mutual interval between the first phases in the stacking direction in the structure is 4 μm or more and 15 μm or less. In the aluminum alloy composite material for a heat exchanger having a sacrificial material layer, a core material layer, and a brazing material layer, the sacrificial material layer contains 0.5 to 5 mass% Zn, and the balance is made of Al and inevitable impurities. A sacrificial material layer, wherein the core material layer is 0.05 to 2.0 mass% Mn, 0.003 to 1.2 mass% Cu, 0.05 to 1.2 mass% Si, and 0.05 to 0. 4 mass% core layer der remainder containing V being Al and inevitable impurities is, and the Oite V high concentration first solid solution phase and V low concentration second solid solution phase in the core layer Is an aluminum alloy composite material for heat exchangers having a structure in which the layers are alternately laminated in the thickness direction of the composite material, and the interval between the first phases in the lamination direction in the structure is 4 μm or more and 15 μm or less. In the aluminum alloy composite material for a heat exchanger having a sacrificial material layer, a core material layer, and a brazing material layer, the sacrificial material layer contains 0.5 to 5 mass% Zn, and the balance is made of Al and inevitable impurities. It is a sacrificial material layer, and the core material layer is 0.05 to 2.0 mass% Mn, 0.003 to 1.2 mass% Cu, 0.05 to 1.2 mass% Si, 0.05 to 0.00. remainder containing 4 mass% of V and 0.03～0.3Mass% of Ti is Ri core layer der of Al and unavoidable impurities, and the first solid solution phase high Oite V concentration in said core layer And a second solid solution phase having a low V concentration are alternately stacked in the thickness direction of the composite material, and the interval between the first phases in the stacking direction in the structure is 4 μm or more and 15 μm or less. An aluminum alloy composite for a heat exchanger. A member is manufactured using the aluminum alloy composite material according to any one of claims 1 to 3, and the member is brazed and heated at a temperature of 560 to 585 ° C. vessel.